In Drosophilia, the gene for red eyes, R, is dominant for the gene for white eyes, r. This is sex-linked Determine the possible genotype and phenotype ratios expected from a cross between, (a) heterozygous female and red-eyed male, (b) a heterozygous female and a white-eyed male, (c) a homozygous dominate female and a redeyed male, and (d) a homozygous dominate female with a white-eyed male.
Let XR stand red-eyed gene and Xr for white.
Heterozygous female would be XR Xr, and red-eyed male would be XR Y. Do the Punnett square with these genes.
Use the same method for the other combinations.
I hope this helps. Thanks for asking.
Convert the following DNA sequence into its RNA equivalent and then using the genetic code, convert that RNA sequence into the amino acid sequence.
5’–TACTTCTTCAAGACT-3’
For this above DNA sequence, what information is contained in the genetic code for the first and last codon?
For each scenario, we will determine the possible genotype and phenotype ratios expected from the given crosses:
(a) Heterozygous female and red-eyed male:
- Female: X^R X^r (heterozygous)
- Male: X^RY (red-eyed)
- Possible offspring: 50% red-eyed females (X^R X^R), 50% red-eyed males (X^R Y)
(b) Heterozygous female and white-eyed male:
- Female: X^R X^r (heterozygous)
- Male: X^rY (white-eyed)
- Possible offspring: 50% red-eyed females (X^R X^r), 50% white-eyed males (X^rY)
(c) Homozygous dominant female and red-eyed male:
- Female: X^R X^R (homozygous dominant)
- Male: X^RY (red-eyed)
- Possible offspring: 100% red-eyed females (X^R X^R), all female offspring will be red-eyed as the dominant allele is present on both X chromosomes.
(d) Homozygous dominant female and white-eyed male:
- Female: X^R X^R (homozygous dominant)
- Male: X^rY (white-eyed)
- Possible offspring: 100% red-eyed females (X^R X^r), all female offspring will inherit the red-eyed allele from the homzygous dominant female, regardless of the father's allele.
Note: It is important to mention that in Drosophila, red eyes are dominant over white eyes and since the eye color gene is sex-linked, it is located on the X chromosome.
To determine the possible genotype and phenotype ratios expected from different crosses in Drosophila, we need to consider the genetic information provided and the principles of inheritance for sex-linked traits.
In this case, the gene for red eyes (R) is dominant over the gene for white eyes (r), and the trait is sex-linked. This means that the gene is located on the sex chromosome, specifically the X chromosome.
Now let's consider the crosses:
(a) Heterozygous female and red-eyed male:
The genotype of the female is XRXr, and the genotype of the male is XRY. The female produces eggs with either an X chromosome carrying the R allele or an X chromosome carrying the r allele, while the male produces sperm with either the X or the Y chromosome.
Possible genotypes of the offspring: XRXR (female, red-eyed), XRXr (female, red-eyed), XRY (male, red-eyed), and XrY (male, white-eyed).
Phenotype ratio: 2 red-eyed females: 1 white-eyed male.
(b) Heterozygous female and white-eyed male:
The genotype of the female is XRXr, and the genotype of the male is XrY. The female produces eggs with either an X chromosome carrying the R allele or an X chromosome carrying the r allele, while the male produces sperm with either the X chromosome carrying the r allele or the Y chromosome.
Possible genotypes of the offspring: XRXr (female, red-eyed), XrXr (female, white-eyed), XrY (male, white-eyed).
Phenotype ratio: 1 red-eyed female: 1 white-eyed female: 1 white-eyed male.
(c) Homozygous dominant female and red-eyed male:
The genotype of the female is XRXR, and the genotype of the male is XRY. The female produces eggs with the X chromosome carrying the R allele, while the male produces sperm with either the X or the Y chromosome.
Possible genotypes of the offspring: XRXR (female, red-eyed), XRY (male, red-eyed).
Phenotype ratio: All offspring will be red-eyed.
(d) Homozygous dominant female and white-eyed male:
The genotype of the female is XRXR, and the genotype of the male is XrY. The female produces eggs with the X chromosome carrying the R allele, while the male produces sperm with the X chromosome carrying the r allele or the Y chromosome.
Possible genotypes of the offspring: XRXr (female, red-eyed), XrY (male, white-eyed).
Phenotype ratio: All females will be red-eyed, and all males will be white-eyed.
In summary:
(a) Heterozygous female and red-eyed male: 2 red-eyed females: 1 white-eyed male.
(b) Heterozygous female and white-eyed male: 1 red-eyed female: 1 white-eyed female: 1 white-eyed male.
(c) Homozygous dominant female and red-eyed male: All offspring will be red-eyed.
(d) Homozygous dominant female and white-eyed male: All females will be red-eyed, and all males will be white-eyed.